The present disclosure sets forth a jaw mounting mechanism which assists in mounting a work piece on a machine tool for repetitive machining. It is particularly adapted for use in the chuck jaws of a machine tool such as a milling tool or lathe. When mounted in the machine tool, the jaws are opened or closed to repetitively grasp a work piece. Through the use of the present invention, the jaws are equipped with an insert which can be installed for a production run, removed and thereafter reinstalled without requiring measurements or other steps to align the chuck jaws. The jaw insert of the present disclosure is registered on each occasion.
In the context of a machine tool, the work piece to be cut is usually rotated about-an axis of rotation which is defined by a chuck mechanism. Generally, chucks can have dependent or independent jaws. The apparatus of the present disclosure is especially useful for both types of jaws wherein the work piece to be machined is changed periodically. More specifically, the chuck is normally constructed with three or four jaws. They slide on radially directed ways which enable the jaws to move towards or away from the centerline axis of the chuck. When they move radially inwardly this enables a smaller work piece to be held. In a chuck equipped with dependent jaws, they move in unison radially inwardly or outwardly. This is typically used for grasping round stock such as pipe, bar stock, and the like. The dependent jaws thus grasp the round work piece at three or four points around the periphery, centering the work piece. This enables the machine tool to be switched off, one work piece removed, and the next work piece inserted without making measurements. The work piece is therefore held concentric about the axis of rotation so that machining can be started quickly. In this particular instance, it is very important that the inserts on the jaws contact and grasp the work piece around the periphery.
When a set of jaws is used for machining one work piece, it is common to machine a conforming step on the jaw inserts. When another work piece is handled, it may be necessary to use a new set of inserts. The jaw inserts are constructed so that they can be machined to conform with a different work piece. As a result of this, it may be necessary to use a set of inserts for a long production run, store the inserts and then retrieve them for another production run of the same work piece. Consider as an example a set of inserts which are machined to grip a four inch OD bar; such inserts would not readily fit on one inch bar stock. Different inserts would be required for that.
When switching inserts in the jaws of the chuck, it is necessary to align the inserts with respect to the individual jaws. Especially where the jaws are dependent, the inserts must all be registered with respect to a particular reference. This is solved in a dependent jaw mechanism in the situation where the jaws move on the ways radially. If the chuck is properly aligned, the jaws will properly close down on different sizes of bar stock and hold it perfectly. That is, whether the bar stock is small or large in diameter, movement of the jaws clamps and holds a small or large work piece at a concentric location on the machine tool. Continuing however, if it is necessary to switch inserts, all three of the new inserts in a three jaw mechanism must be registered so that consistent movement with regard to the centerline axis of the rotating apparatus is achieved. This requires careful alignment. The present disclosure sets forth a mechanism which enables sacrificial inserts to be mounted on the chuck jaws of a machine tool which accomplishes alignment without the use of tools. In one aspect of the present disclosure, the individual inserts are constructed so that a sacrificial insert can be positioned properly in space with respect to jaw mounting mechanism. More particularly, registration surfaces are provided along with a lock mechanism so that the inserts can be removed or reinstalled without making measurements.
In one regard, the present disclosure sets forth a sacrificial insert which terminates in a mounting post which is equipped with a key slot on the external surface of a mounting stem or post. A flat is formed on the mounting post and extends along one side of the mounting post until it abuts against a conforming lock pin groove. The groove for the lock pin is at an angle with respect to the flat. When a lock pin is properly located in the chuck jaw, this enables the insert to be rotated so that the lock pin is secured in the conforming groove and secures the insert against movement. It cannot be retrieved accidentally. In addition to that, the post is provided with a dimple which enables a pointed set screw to be threaded against the post to lock the post against rotation. Last of all, the post terminates at a shoulder on the sacrificial insert which shoulder provides a registration surface. This assures that the insert extends by a fixed and uniform distance from the jaw on which it is installed. Therefore, the sacrificial insert can be installed without making measurements and can then be used at different times. On each installation no measurements are required to perfect the installation.